Electron discharge tube amplifier



July 1, 1947. LEHMANN 2,423,106

' ELECTRON DISCHARGE TUBE AMPLIFIER Filed April 13, 1945 L(R) w e a l l I n L+ v 150 c E-l' a bvmvrdx. 65944? 15907109) Patented July 1947 Gerard J.

Lehmann,

Boulogne-Billancourt,

France, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application April 13, [2743, Serial No. 482,908 ln -Francefieptember 12, 1941 3 Claims.

The present invention relates to improvements in devices which employ circuits having a socalled negative resistance characteristic.

The basic object of this invention is to provide a device having a circuit with a negative resistance characteristic which is capable of amplifying direct current or low frequency currents.

A more specific object of the invention is to provide an apparatus of this type for amplifying direct or low frequency currents by applying them to a condenser connected in parallel (Cl. Til-95) with a resistance such as a dynatron. the characteristic of which is periodically changed from negative to positive.

Other and more detailed objects of the invention will be apparent from the following disclosure when taken in connection with the attached drawings.

This invention resides substantially in the combination, construction, arrangement and relative location of parts, all as will be described in detail below.

Referring to the drawings,

Figure 1 is a diagrammatic circuit illustration by which the principle underlying this invention may be explained;

Figure 2 is a graph showing curves illustrative of this principle; and i t Figure 3 is a diagrammatic illustration of one embodiment of the invention herein disclosed.

Super-regenerative amplifiers are now used in which a circuit having a negative resistance characteristic functions to provide large and rapid increases in the rate of oscillations thereof. Such amplifiers are used in the reception of high frequency radio waves by varying the resistance of the circuit so as to periodically change it from a state of positive resistance to one of negative resistance. The amplitude of the oscillation generated during the periods of negative resistance depends upon the amplitude of the currents to currents in particular.

a combination the voltage at the terminals of the capacitor is in an unstable condition. Any impulseapplied to this capacitor is causing exponential increase of this voltage which will have the same polarity as that of the impulse and will increase with a rapidity directly proportional to the amplitude of the voltage of the impulse.

According to a feature of this invention by applying the voltage to be amplified to the capacitor C and making the resistance R alternately negative and positive, there is obtained at the end of each cycle a voltage which depends in polarity and magnitude upon the initial voltage, but which is greatly amplified.

It is thus possible to provide an apparatus which permits amplification of currents without change in polarity, that is amplification of direct It is possible to connect in series with the apparatus just described, an integrating instrument that will give indications depending upon the variations of the voltage applied to the capacitor C.

Figure 2 diagrammatically illustrates by way of example a series of curves of the voltage conditions at the terminals of the capacitor C in combination with the negative resistance R as illustrated in Figure 1 for different values of applied voltage at the instant of application. As illustrated in Figure 2, the voltages applied to the terminals of the capacitor C are plotted as ordinates and time intervals are plotted as abscissae.

There is illustrated in Figure 3 one example of an embodiment of this invention in an amplifier circuit, As before, the capacitor is indicated at C, but in this case the negative resistance is provided by the multi-electrode vacuum tube L(R) be amplified. By this apparatus it becomes practicable to obtain high amplification.

In accordance with the features of this invention direct or low frequency voltages are amplified by employin a resistance that is changed pe-- riodicaly from a-negative to a positive state by the use of an auxiliary oscillator. In this arrangcment an unstable condition is created which increases exponentially with the polarity of the applied voltage to be ampified and with a raridtv that is proportional to the amplitude of the applied voltage.

Referring to Figure 1, a capacitor C is disposed in parallel with a negative resistance R. In such 5 which may be of the dynatron type. R represents a positive resistance shunted across the capacitor C acting to return the capacitor C to a steady state condition at the end of each cycle. An alternating current voltage such as provided by a super-regenerative oscillator is ,applied to one grid of the vacuum tube, as for example across the terminals alpha. The voltage to be amplified is applied to another grid of the vacuum tube, as for example the terminals marked I50 in Figure 3. An integrating instrument is connected in series with the positive resistance R and a suitable current source, as shown, across the'capacitor C. With this circuit combination the alternating current voltage applied across the terminals alpha periodically renders the negative resistance characteristic of the dynatron L(R) effective to impart a negative resistance characteristic to the circuit CWR, as indicated in connection with Figure 1, to amplify direct or low frequency currents applied across the terminals marked 150 volts, without change of polarity. These amplified currents appear across the terminals of the capacitor C and may be read on the indicating instrument or otherwise employed depending upon the use to which the equipment is to be put.

It will be apparent from the above description that those skilled in the art will readily perceive modifications of the embodiment herein disclosed, and I do not, therefore, desire to be strictly limited to this disclosure as given for purposes of illustration, but rather to the scope of the attached claims.

What is claimed is:

1. A circuit combination for amplifying direct and low frequency currents including an electronic valve capable of operation under conditions of negative resistance and including an anode and a plurality of grids, a capacitor shunted across the anode and the cathode of said valve, an integrating circuit shunted across said capacitor including a positive resistance, an integrating instrument and a source of potential, all connected in series,.a high {frequency current feed circuit for said valve extendin from the grid nearest said cathode to said cathode thereof, and an input circuit for direct and low frequency current extending from the grid next removed from said cathode to said cathode.

2. A circuit combination for amplifying direct and low frequency currents comprising a dynatron vacuum tube having a cathode, an anode and a plurality of grids, a condenser shunted directly across said anode and said cathode, a circuit for the current to be amplified extending from said cathode to a first grid, and a high frequency circuit extending from said cathode to the grid nearest said cathode. said dynatron having a negative resistance characteristic rendered alternately eifective by said high frequency cir- Cul 3. A circuit combination according to claim 2, including a source of potential and a positive resistance connected in series and shunted across said condenser.

GERARD J. LEHMANN.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,971,347 Hyland Aug. 28, 1934 2,093,781 Roberts Sept. 21, 1937 2,072,945 Famham Mar. 9, 1937 

